The former US ambassador was spotted urinating in a street in Notting Hill, west London after a late night visit to the home of former Conservative chancellor George Osborne.
The Daily Mail, external reported pictures of Lord Mandelson being caught short and relieving himself against a wall in the upmarket London area after leaving Osborne’s home.
The council said street enforcement officers were not at the scene of the alleged urination, so could not issue a fine at the time.
But, given the images and public quotes made about the offence, the authority said it was looking to issue a fine.
Without an official address for Lord Mandelson, the fine has not yet been issued.
The fixed penalty notice carries a fine of up to £300, reduced to £150 if paid within two weeks.